JPH0466810A - Detector of moving speed of object - Google Patents

Abstract

PURPOSE:To enable speed detection without a failure by reducing random noise on a distance measurement result and also by resetting an integration result when the distance measurement result or its integration result is not judged to be appropriate for the speed detection. CONSTITUTION:A driver 13 drives an infrared ray emitting diode (IRED) 12a contained in a distance measuring optical system 12 and radiates the IRED 12a a plurality of times with equal intervals by control of a CPU 11. A distance calculating circuit 14 calculates a distance l to an object 10 based on an output of an optic position detecting element 12d. An integration circuit 15 sequentially integrates distance measurement results in the calculating circuit 14. By repeating distance measuring operation and integration operation, highly accu rate detection of speed which is not influenced by random noise is possible. A determining circuit 17 determines that information is not appropriate for speed detection if the distance information outputs an extremely far result or speed information outputs an extremely rapid result and resets the integration operation in the integration circuit 15. Thus execution of erroneous speed detec tion is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to, for example, a moving speed detection device for a subject, and more specifically, to automatic focus photography of a camera that drives a photographing lens to a focus position based on a focus detection output. The present invention relates to a subject moving speed detection device that is applied to a photographic device, etc., and detects the moving speed of the subject in order to prevent out-of-focus due to movement of the subject in the optical axis direction of the photographic lens.

[Prior Art] Conventionally, when attempting to photograph a subject moving in the optical axis direction of a photographic lens, there has been a drawback that a focus shift occurs as the subject moves during the release time lag.

Therefore, in order to prevent this focus shift, for example, Japanese Patent Application Laid-Open No. 159817/1983 discloses that distance measuring operations are performed multiple times in response to the Lullize signal, and the position of the subject at the start of exposure is predicted and the photographing lens is adjusted. A drive device is disclosed. Furthermore, in fields other than cameras, a method has been proposed in which infrared rays are projected onto an object to be measured and the moving speed of the object is detected based on the reflected signal, as shown in Japanese Unexamined Patent Publication No. 62-232571. has been done.

Here, a conventional speed detection device will be explained using the above-mentioned Japanese Patent Laid-Open No. 63-159817 as an example.

In FIG. 7, 1 is a subject, and 2 to 4 are a distance measuring optical system, a light emitting element driving circuit, and a light emitting element driving circuit, respectively, which constitute a distance measuring device.
This is a distance calculation circuit.

That is, when an infrared light emitting diode (IRED) 2a included in the ranging optical system 2 is driven by the light emitting element drive circuit 3, the light from the IRED 2a or the light projecting lens 2b is
The light is projected onto the subject 1 through. The light projected onto the subject 1 is reflected there, then condensed by a light receiving lens 2c, and formed into an image on a optical position detection element (PSD) 2d. Then, from the PSD 2d, a signal current 1. , I2 are output.

Then, by processing these signal currents II and I2 by the distance calculating circuit 4, the distance to the subject 1 is determined.

In the speed detection device, the distance measuring operation as described above is repeated at predetermined time intervals according to the timing circuit 5.

After each distance measurement result is stored in the distance data storage circuit 6, the moving speed of the subject 1 is detected by calculating how far the position of the subject 1 has been displaced within a predetermined time.

Note that this speed detection device is equipped with a dedicated function determination circuit 7 consisting of an order determination circuit 7a, a linear function determination circuit 7b, and a quadratic function determination circuit 7c in order to determine speed changes as well. It included a distance prediction calculation circuit 8 for predicting the subject distance at a time point (at the start of exposure), a control circuit 9 for controlling them, and the like.

[Problems to be Solved by the Invention] The conventional speed detection device described above is effective when the distance measurement time is negligibly short and there is no error in the distance measurement result.

However, in reality, these must be taken into consideration, and there are also the following drawbacks. That is, in order to accurately determine the order of the function of the motion speed of the subject 1 from the distance data, a complicated circuit is required, which is expensive. Furthermore, if a one-chip microcomputer (for example, a CPU) is used to perform calculations on software, the calculation time cannot be ignored, and the speed of an object moving at high speed, such as a car, cannot be detected. becomes impossible.

For these reasons, what is required in a speed detection device is a distance measuring device that has extremely small distance measurement errors and can perform distance measurement operations at high speeds. However, electronic circuits always contain noise, and it is not easy to create an ideal distance measuring device.

On the other hand, the applicant of the present application has already made a proposal (for example, see Japanese Unexamined Patent Publication No. 132110/1983) to realize highly accurate autofocus by the noise canceling effect of integration.

However, as in this proposal, the distance measuring method in which the IRED emits light many times results in a long time lag, so it is not suitable for a speed detection device.

FIG. 8 shows a general speed detection operation using a conventional distance measuring method.

That is, when it is difficult to ensure accuracy with just one distance measurement operation, noise components that randomly appear in the distance measurement results can be canceled out by performing the distance measurement operation a plurality of times. However, as shown in FIG. 8, if the ranging operation is performed multiple times (for example, four times in this case) at the timing (a), a time lag will occur. Furthermore, since the distance to the subject changes during the four distance measurement operations, it is difficult to say that this is an effective method for distance measurement of a moving object.

Furthermore, a certain amount of time lag occurs during the distance calculation operation for obtaining accurate distance measurement results from the aforementioned four distance measurement results at the timing (b).

Following the timing of (b), the distance measurement operation is performed four times at the timing of (c), which is the same as the timing of (a), and (
After performing a distance calculation operation to obtain an accurate distance measurement result from the results at timing d), if you try to calculate the moving speed of the subject from the results of those two calculations, the ), which requires a very long speed detection time.

Furthermore, since the distance is measured from a moving object, the advantage of repeating distance measurement many times is lost due to changes in the moving object during distance measurement.

Therefore, it was expected that it would be very difficult to perform distance measurement with high precision and shorten the time lag that tends to occur, and to detect the speed of the subject using the same concept as before.

Furthermore, if something like the re-ignition noise of a fluorescent lamp happens to occur at timing (a) or timing (c), and an error occurs in the data, the speed detection method described above will detect the noise twice. Since one of the distance measurement results becomes meaningless, the error in speed calculation becomes large. However, there is no way to detect that the data has been disturbed by noise, so when applied to moving object distance measurement with a camera, for example, speed calculations may not be performed correctly until the finished photo is seen. I had no way of knowing that it had happened.

Originally, in the case of active autofocus, it is not possible to measure distance with sufficient accuracy at long distances, regardless of the presence of noise, so accurate speed calculations may not be performed.

Therefore, in such cases, rather than blindly performing uncertain velocity calculations, it is better to issue a warning before performing velocity calculations, or wait until the subject approaches a short distance that can be reliably measured with high accuracy. It can be said that it is a more friendly design not to perform speed calculations.

The same can be said of moving objects that are too fast to be photographed.

Furthermore, if you start speed detection without the subject definitely being in the distance measurement frame, as soon as the subject enters the distance measurement frame, the distance result or output changes from output to finite distance output. . Then, the subject speed in this case is ■
Therefore, there was a possibility that the speed would not be detected correctly.

This invention was developed in view of the fact that the above-mentioned distance measuring devices always have distance measurement errors and it is difficult to accurately detect the speed of the object. It is an object of the present invention to provide a device for detecting the moving speed of a subject, which is easy to use, and does not cause speed detection failures.

[Means for Solving the Problems] In order to achieve the above object, the object moving speed detection device of the present invention includes a light projecting means for projecting light onto the object, and a distance measuring means for receiving reflected light from the object and outputting a value dependent on the object distance; a light projection control means for repeating light projection by the light projection means a plurality of times at predetermined time intervals; an integrating means for integrating the output of the distance measuring means based on the light projected by the light projecting means; a speed calculation means for calculating the moving speed of the subject with respect to the optical axis direction of the light projecting means from the output of the integrating means; It is comprised of a determining means for determining whether there is an abnormality in the output of the ranging means or the integrating means, and an initializing means for initializing the output of the integrating means in accordance with the determination result of the determining means.

[Function] With the above-described means, the present invention can easily reduce random noise that appears in the distance measurement results, and can also be used in cases where the distance measurement results or their integration results are not determined to be appropriate for speed detection. Since it is possible to prevent erroneous speed detection by resetting the integration result, failure-free speed detection can be easily realized.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration of a moving speed detection device for a subject according to the present invention.

That is, the CPU 1 is in charge of controlling the entire device, and a driver 13, a distance calculating circuit (AF circuit) 14, an integrating circuit 15, and the like are connected to the CPU II. In addition, the distance calculation circuit 14 and the integration circuit 15
is turned on (closed) by the CPU 1 above.
/off (open) switches SWI, SW2, and a signal inversion circuit 1 connected in series to this switch SW2.
6 or so are installed in parallel.

Furthermore, this object moving speed detection device is configured to use the output (distance information) of the distance calculation circuit 14 or the C integration circuit 15.
A determination circuit 17 that determines whether the output (speed information) is suitable for later speed detection, and a warning circuit that issues a warning when it is determined that it is not suitable. has been done.

The driver 13 drives an infrared light emitting diode (IRED) 12a included in the ranging optical system 12,
Under the control of the CPUI 1, the I RED 12a is caused to emit light multiple times at the same time interval.

The distance measuring optical system 12 includes the IRED 12a and the IR
A light projecting lens 12b that projects the light (infrared light signal) from the ED 12a toward the subject 10, a light receiving lens 12c that collects the reflected light from the subject 10, and a light receiving lens 12c that collects the light reflected from the subject 10. signal current according to the incident position of the reflected signal light.

The optical position detection element (PSD) 12d generates I2.

The distance calculation circuit 14 extracts the signal light component from the steady light component based on the output signal of the PSD 12d based on the light emission of the IRED 12a, that is, under the control of the CPU 1, and calculates the signal light component in an analog manner. This is to find the distance g.

The integrating circuit 15 sequentially integrates the distance measurement results in the distance calculation circuit 14. In this integrating circuit 15,
When the switch SWI is turned on under the control of the CPU 1, the distance measurement result is positively integrated, and when the switch SW2 is turned on, the distance measurement result is negatively integrated. It is designed to be a positive integral.

The determination circuit 17 performs long-distance determination, that is, when the distance measurement result (distance information) in the distance calculation circuit 14 is too far to be suitable for speed calculation, or high-speed determination, that is, the integration result ( If the speed information) is extremely fast or there is a possibility of noise being mixed in, it is determined and an instruction to reset/sort the integration operation in the integration circuit 15 is output. Further, at the time of the above-mentioned reset, an instruction is outputted to the warning circuit 18 to issue a warning.

The CPU 1.1 includes a driver 13 and a distance calculation circuit 14.
In addition to controlling the driving timing of the integrating circuit 1,
5 output V. The moving speed of the subject 10 in the optical axis direction is calculated based on the UT.

Further, the CPU II is configured to control the integration timing (switching of the switches SWI and SW2) in the integration circuit 15. That is, the CPU 11 uses the driver 1
When the IRED 12a is made to emit light via the switch S W 1. .

It is designed to control opening/closing of SW2.

FIG. 2 shows the effect of integration in the integration circuit 15.

Here, the vertical axis is the subject distance (ρ), and the horizontal axis is time (1).
The straight line (N(t)) shows the relationship between Ω and t when the subject 10 moves at a constant speed.

In this embodiment, positive integration or negative integration is actually performed by one integrating circuit 15 by alternately turning on and off the switch 5WISW2. A case will be described in which the first three distance measurement results are integrated by one integrating circuit, and the next three distance measurement results are integrated by another integrating circuit.

In FIG. 2(a), time 0. t, 2t.

Each distance measurement result at 3t, 4t, and 5t is DI
, I) 2 , I3, I4, I9, I6,
An example is shown in which there is no error in the distance measurement results.

In this case, the integration result for the distance measurement results ρ1, I2, and I3 is the area of the upper right diagonal line S1, and the distance measurement result 114
, I9, and I6 are shown in the upper right diagonal area S2.
The area will be .

Difference between area S and area S2 at this time (difference in integral output)
Then, the area shown by the diagonal line S downward to the right on the area S1 is obtained. This area S3 becomes speed information.

That is, as shown in the figure, for example, ρ, -12, D 2
-11, D 3-10, ρ4-9, g5-8, p6=7
Assuming that the subject 10 approaches one by one during the unit time t, the area S1 and the area S2 are S, -10+11+12-33, respectively.
(1) S2-7+8+9-24 (2) Therefore, the area S is S, -3, -32-9 (3).

From this result, the difference in the start timing of the integration of the areas Sl and S2 is 3t, and the number of integrations is 3 each, so the speed ■ is v = S s / 3 t X 3-9 / 9
It can be calculated as t-1/t-(4).

Figure 2(b) shows times 0, t, 2t, 3t, 4t, 5t.
Each distance measurement result g 1, g 2, g ′3, ρ−4
, Jl'-s, and 1l-6 are shown as an example in which random noise is added.

In this case, due to the noise cancellation effect due to integration, S-3”
"S-+ S-2→S3-9...(5). Therefore, similarly to equation (4) above, the speed detection that the position changes by one per unit time t is This is possible despite the inaccuracy of the results.

Next, we will explain the operation of the present invention, which basically uses the same concept as the distance measurement method based on the difference between two integral outputs explained with reference to FIG. 2, and enables more accurate speed detection. .

In particular, in the case of so-called active AF, in which distance measurement is performed by projecting IRED light onto a subject, the farther the subject is, the worse the S/N ratio and the worse the accuracy.

Therefore, as shown in FIG. 2, the integration operation is performed for each distance measurement result g1. When the long distance side of Ω2 + fl 3 is performed as one set, and each distance measurement result (14, It6.Ilb
There is a large difference in accuracy between the two integration results compared to when the near-distance side of is performed as one set.

Therefore, in the present invention, for example, the first distance measurement result g1 is guided to the integration circuit 15 so as to be an integral output in the positive direction, and the second distance measurement result p2 is led to the integral output in the negative direction. Then, the signal is inverted and guided to the integrating circuit 15, so that the third distance measurement result g3 becomes an integrated output in the positive direction again... In this way, the integration in the integrating circuit 15 is performed every time the distance measurement operation is performed. Integral operation is performed by switching the direction of . In this way, by integrating the odd-numbered distance measurement results in the positive direction, and conversely integrating the even-numbered distance measurement results in the negative direction, it is possible to finally obtain a signal based on speed information. .

In addition, by switching the direction of integration, there is no need to prepare and store the two integration results of the area S1°S2 as in the case explained with reference to FIG. The integration circuit enables calculations similar to the above equation (4).

FIG. 3 specifically shows the timing of the ranging operation and the integrating operation according to the present invention.

That is, for each distance measuring operation, the integration circuit 15 repeats the integration operation in the positive direction and the integration operation in the negative direction at the timing shown in the figure. As a result, as shown in the figure, at the time when the even-numbered integral operation is completed, a signal based on the speed information is output as the integral output VoUT.

Here, following the example of FIG. 2 mentioned above, this speed calculation operation will be explained.
43D4+F5-ρ6)/ is -1/l (6), and the same result as the above equation (4) is obtained.

Additionally, compared to conventional speed detection devices (see Figure 8), this method eliminates the need for the process of calculating distance, so when speed detection is performed in the same amount of time, more integration is required. We can expect a noise canceling effect. Furthermore, since changes in the subject position for each distance measurement operation are taken into account from the beginning, it is possible to detect speed with much higher accuracy.

The integral operation described above will be specifically illustrated with reference to FIG.

That is, the CPU II uses the IR via the driver 13.
Each time ED12a emits light, switch SWI
, SW2 are turned on and off, and the calculation output of the distance calculation circuit 14 is supplied to the integration circuit 15. At this time, the distance measurement results for the even-numbered light emissions are input to the integration circuit 15 via the signal inversion circuit 16 so that the integration operation in the opposite direction to the distance measurement results for the odd-numbered light emissions is performed.

With such a configuration, one integral circuit]
Integral operation in the opposite direction has been realized.

Next, an embodiment of the present invention will be further described.

FIG. 4 shows details of the configuration of the distance measuring optical system 12.

This distance measuring optical system 12 constitutes a known single point distance measuring device, and is of a so-called active type that projects AF light onto the subject 10.

Now, when the IRED 12a emits light, the light becomes AF light and is projected onto the subject 10 via the projection lens 12b. Then, this AF target is reflected by the subject 10 and focused through the light receiving lens 12C, thereby forming an image on the PSD 12d.

In this case, the incident position X of the reflected light is expressed as a function of the subject distance g according to the principle of triangulation as shown by the following equation.

Here, S is the principal point distance M (baseline length) between the light projecting lens 12b and the light receiving lens 12c, and f is the distance between the principal points of the light projecting lens 12b and the light receiving lens 12c.
The PSD 12d is arranged at this position with a focal length of .

From the PSD 12d, two current signals 1. , I2 are output. The total signal photocurrent is Ipo
If the length of the PSD 12d is t, then g can be expressed as in the following equation.

...(10) Here, a is a line parallel to the line connecting the light emission center of the IRED 12a and the principal point of the light projecting lens 12b.
This is the length from the point where it crosses the PSD 12d to the end of the PSD 12d on the IRED 12a side when extended from the principal point of the PSD 12d.

FIG. 5 shows the output signal 1. of the PSD 12d. , I2 shows a specific circuit configuration for integrating distance information in the integrating circuit 15.

In FIG. 5, 21.22 is the output signal 1.22 of the PSD 12d generated in response to the light emission of the IRED 12a. , I2 with a low input impedance and amplifies it, and 23.24 is the amplified current 1. ,
This is a compression diode for compressing only I2.

2526 is a buffer, compression diode 23.24
This is for guiding the compressed voltage at the voltage to the differential arithmetic circuit 30 consisting of the NPN transistors 27 and 23 and the current source 29.

Here, when the operation of the differential arithmetic circuit 30 is explained using the symbols in the figure, the following relational expression (15) holds true. Note that Is is transistor 2
7.28 and the reverse saturation current of the diode 23.24, and VT is the thermal voltage.

Moreover, the current 1a and the current Ib are I a + l b = I o+ ”
'(13), the above (11) (12
), from equation (13), the signal current Ia is obtained which is proportional to the reciprocal of the object distance Ω.

Further, numeral 31 in the figure is a current source, and the current 1c caused by the current source 31 has the following relationship: Ic -10,+Id.=(16). Therefore, the current lx flowing through the compression diode 32 is lx-! The relationship a-1c holds true.

Therefore, from equations (10) and (14) above, ...(17) becomes.

On the other hand, a current I is supplied to the compression diode 33 by a current source 34.
The compressed voltages of the compression diodes 32 and 33 are inputted to a circuit 37 having the same type as the differential arithmetic circuit 30 described above through buffers 35 and 36t, respectively.

Therefore, the output current If of the differential arithmetic circuit 37 consisting of the NPN) transistor 39°40 and the current source 41
i then becomes as follows, taking into account that the compression diode 3233 generates a voltage with reference to the power supply side. Therefore, from equation (17) above, the current is 1.17
Ω (19) is obtained as a current signal proportional to the subject distance g.

In other words, each time the IRED 12a emits light, the switch SWI or SW2 is turned on by a timing signal, and the current IΩ, which depends on the object distance Ω, is integrated by the integrating capacitor 45 of the integrating circuit 15. .

As mentioned above, switches SWI and SW2 are IRED
IRED1 is switched sequentially in synchronization with the light emission of IRED12a.
2a, for example, the switch SWI is turned on and the switch SW2 is turned off, and when the light emission is an even number, for example, the switch SW2 is turned on, and the switch SW2 is turned on.
I is turned off, and when the IRED 12a does not emit light, both switches SWI and SW2 are turned off. In addition, the integrating capacitor 45 is connected to the IRED12
Prior to the light emission of a, the reset circuit 46 resets the light to the initial state. For this reason, I
When the RED 12a starts emitting light, the signal current 1g that depends on the subject distance g is poured into the integrating capacitor 45 by closing the switch SWI in the odd-numbered light emission of the IRED 12a. As a result, the output of the output terminal 47 is changed in ten directions as shown in FIG. 3 described above.

On the other hand, in the even-numbered light emission of the IRED 12a, the switch SW2 is closed, so that the signal current Iρ, which depends on the object distance p, is transferred from the integrating capacitor 45 by the action of the current mirror circuit 50 consisting of PNP transistors 48 and 49. washed away. Then, as shown in FIG. 3, the output of the output terminal 47 is changed in one direction. In this case, the current mirror circuit 50 functions as the signal inverting circuit 16 of FIG. 1 by changing the direction in which the signal current ρ flows by turning the switches SWI and SW2 on and off.

Now, according to Fig. 2 above, the subject position Ω (1) is determined by the velocity V, II' (t) = v-t +, Q 1
...(20).

Also, from the above equations (19) and (20), the current IΩ is: 1 Ω −A −g (t) −A (ff l−V −t)
−(21). However, A is a constant.

Therefore, assuming that the capacitance of the integrating capacitor 45 is C, the logical calculation formula for determining the speed (2) using the above-mentioned method is as follows.

The output terminal 47 outputs an integrated value in which positive integrals and negative integrals are alternately repeated with Vref as a reference.To make it easier to understand, we will first explain the integral in the positive direction, that is, the positive integral. When the integrated voltage value is determined as VOUTI, it becomes V 0LITI. Here, T is the sum of each integration time t a − t e.

Also, the integral voltage value of the negative integral, that is, the negative integral.

When calculated as LIT2, the integration time Cma voltage V 0
Like LIT□, it has T, and the voltage is V. ul(2 sentences 1 and the timing is shifted by Δt (from this, 0uT2 = 1 '1Ω・dt −[, p+(T+Δt ) −−(T+Δt)2j)+
Δt 10−Δt2 ko...
It can be expressed as (23).

As a result, the output terminal 47 receives +1 the voltage value V 0
The difference between LIT□ and the voltage value V0IJT2 will be output, and its integrated voltage V. 0 is V OUT ”” V 0IJTI V 0LIT
28 ・■・Δt−T (24).

Therefore, based on this result, the speed V is as follows. However, D is a constant.

As described above, the speed V can be easily determined from the integral output V OUT as the speed information that finally appears at the output terminal 47.

In this way, after the even-numbered ranging operation, the integration result as speed information always appears at the output terminal 47. Therefore, at this timing, the voltage V appearing at the output terminal 47. The above-described high speed determination is performed by determining whether the speed is too high from the UT.

That is, the voltage V. Ul is sent to the determination circuit 17 and input to the positive terminal of the comparator 51. Comparator 5
1 has a reference voltage Vref for high-speed determination.
v is supplied. In this case, as shown in equation (24) above, even if the speed V is the same, the voltage V increases as the integration time T becomes longer. U□ becomes larger. Therefore, as the integration time T becomes longer, it is necessary to increase the reference voltage Vrefv.

The output of the comparator 51 is sent to one input terminal of a gate circuit 52 that constitutes a timing circuit. The other input terminal of this gate circuit 52 has a timing signal T I
M v is supplied. Therefore, at the timing when the even-numbered distance measuring operation is completed, the gate circuit 52
is opened, the output of the comparator 51 (H/
An output (L/H) corresponding to L) is output to the NOR circuit 53.

On the other hand, the current IN flowing through the resistor 38 for each integral operation
By determining 2, the long-distance determination described above is performed. In this case, the current Ig2 flowing through the resistor 38 is: IN 2-1o2 I#-Ioz A”N
``' satisfies the relationship (26), and the object 10 is too
It is set so that it becomes smaller when the distance is far. Therefore, in the case of long-distance determination, the magnitude of this current IN2 is determined.

That is, the voltage VL2 corresponding to the magnitude of the voltage drop across the resistor 38 due to the current 11)2 is sent to the determination circuit 17 and input to the positive terminal of the comparator 54.

A reference voltage Vrefρ for long-distance determination is supplied to the negative terminal of the comparator 54.

The output of the comparator 54 is sent to one input terminal of a gate circuit 55 that constitutes a timing circuit. The other input terminal of this gate circuit 55 has a timing signal TIMΩ
or will be supplied. By opening the gate circuit 55 at the timing when each ranging operation is completed, an output (L/H signal) corresponding to the output (H/L signal) of the comparator 54 is output to the NOR circuit 53. It is now possible to do so.

When a signal is generated from either one of the gate circuits 52 and 55, the integrating capacitor 4 is output from the NOR circuit 53.
A reset instruction signal for initializing 5 is output.
In other words, the voltage V 0117 becomes higher than the high-speed reference voltage Vrefv, and the comparator 51 outputs an H value due to high-speed judgment.
When the signal is output, or when the input voltage VL2 becomes larger than the long-distance reference voltage Vrefp and the comparator 54 outputs an H signal based on the long-distance determination, a signal is output from the gate circuit 52.55 based on this output. is H
The signal is changed into a signal and output to the reset circuit 46. This H signal is also sent to the warning circuit 18, so that the warning circuit 18 performs a warning operation.

Note that the warning operation in the warning circuit 18 may be controlled by determining the H signal from the NOR circuit 53 by the CPU 11.

FIG. 6 shows the reset operation in the above configuration.

That is, in the second distance measuring operation, it is assumed that, for example, the input voltage VL2 becomes greater than the long distance reference voltage Vref(l) and the comparator 54 outputs an H signal.

Then, the gate circuit 55 outputs an L signal, and in response, the NOR circuit 53 outputs an H signal. Therefore, by operating the reset circuit 46 to initialize the integrating capacitor 45, the output V0LIT of the integrating circuit 15 is reset. Then, in response to this reset operation, the warning circuit 18 performs a warning operation.

Similarly, if the subject 10 is found to be overspeeding, for example, in the sixth distance measurement result, the voltage V. uT or high speed reference voltage V
refv, and the comparator 51 outputs an H signal. Then, the gate circuit 52 outputs an L signal, and in response, the NOR circuit 53 outputs an H signal. Therefore, by operating the reset circuit 46 to initialize the integrating capacitor 45, the output V OUT of the integrating circuit 15 is reset. Then, in response to this reset operation, the warning circuit 18 performs a warning operation.

As described above, it is possible to easily reduce the random noise that appears in the distance measurement results, and to reset the above-mentioned integration results if the distance measurement results or their integration results are not determined to be appropriate for speed detection. This prevents incorrect speed detection.

In other words, by repeating the distance measurement operation and the integration operation, it is possible to perform highly accurate speed detection that is resistant to noise. When the result is output, it is determined that it is not suitable for speed detection and the integral operation is reset. This makes it possible to prevent erroneous speed detection. Therefore, after resetting, speed detection is performed using only data determined to be appropriate, so speed detection without failure can be easily realized with a simple configuration.

In addition, since a means for warning the reset operation is provided, for example, when the present invention is applied to a camera, etc., if the reset operation continues, the shutter may not be released forever, or an unexpected chance may be missed. It can warn you if there is a danger and it can be very easy to use.

In addition, in the above embodiment, the case where the moving speed of the subject is determined from the integral output, in which the output from multiple distance measurement operations is alternately integrated positively or negatively, has been explained.
Although the present invention is not limited to this, the long distance determination is performed based on the distance information, but the present invention is not limited to this, and it is also possible to perform the long distance determination based on the magnitude of the speed information, for example.

Further, as the comparator, a type that can latch the output may be used in order to clarify the output of the signal of the gate circuit.

It goes without saying that various other modifications can be made without departing from the gist of the invention.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to reduce random noise that appears in distance measurement results and prevent speed detection using extreme output results. With precision,
Moreover, it is possible to provide a moving speed detection device for a subject that can detect the moving speed of a subject at high speed, is easier to use, and does not fail in speed detection.

[Brief explanation of drawings]

1 to 6 show an embodiment of the present invention, in which FIG. 1 is a block diagram schematically showing the configuration of a moving speed detection device for an object, and FIG. 2 outlines an integral operation. 3 is a timing chart shown to explain an example of the integration operation, FIG. 4 is a configuration diagram showing details of the distance measuring optical system, and FIG. 5 is a specific example for integrating distance information. 6 is a timing chart shown to explain the reset operation, and FIGS. 7 and 8 are both shown to explain the prior art and its problems. , FIG. 7 is a block diagram of the speed detection device,
FIG. 8 is a timing chart. DESCRIPTION OF SYMBOLS 10... Subject, 11... CPU, 12... Distance measuring optical system, 12 a-IRED, 12 d-P
S.D. 13... Driver, 14... Distance calculation circuit, 15.
...Integrator circuit, 16...Signal inversion circuit, 17...Judgment circuit, 18...Warning circuit, 23, 24, 32.33
...Compression diode, 29.31.34.41...Current source, 30.37...Differential calculation circuit, 45...Integration capacitor, 46...Reset circuit, 50...Current mirror Circuit, 51.54... Comparator, 52
゜55...Gate circuit, 53...NOR circuit.

Claims (1)

[Scope of Claims] A light projection means for projecting light onto a subject; a distance measuring means for receiving reflected light from the subject by the projection of the light projecting means, and outputting a value dependent on the distance to the subject; light projection control means for repeating light projection by the light projection means a plurality of times at predetermined time intervals; an integrating means for integrating the output of the distance measuring means based on the light projection by the light projection means; and an output of the integrating means. a speed calculating means for calculating the moving speed of the object in the optical axis direction of the light projecting means; a determining means for determining an abnormality in the output of the distance measuring means or the integrating means; and according to the determination result of the determining means. and initializing means for initializing the output of the integrating means.